This poygon shapefile represents Isohyetal lines of equal average rainfall for the Russian River basin in California. These data were derived from an average Average Annual Precipitation Zones layer developed by California Department of Forestry and Fire Protection. Original source data were digitized from a 1:1,000,000 source map compiled by S.E. Rantz, U.S. Geological survey, 1969, 1972. The map is based on data covering the period 1900-1960. Average rainfall zones were created by averaging the rainfall for isohyetals bounding.This layer can be used for watershed analysis and planning in the Russian River region of California.